E-type telephone repeaters ¿ Description, equipment, and testing

THE insertion of repeaters in telephone lines to make up for circuit losses is a very common practice today. The use of negative impedance to overcome transmission loss is an old idea but only recently used to any large extent in the exchange area plant. A series-type of negative-impedance repeater, called the E1 telephone repeater, has found favor in the Bell System and its use has stimulated a demand for still more economical designs including a companion shunt type of negative-impedance repeater. Sufficient laboratory and field trial work has been done on negative-impedance devices to insure that better transmission performance can be obtained, at minimum cost, by using both a shunt element, of the negative-admittance type, and a series type of negative-impedance repeater. Through the use of these new E-type repeaters it is possible to reduce the attenuation and improve the return loss of voice frequency lines so that exchange area trunks can be used as links in a toll connection.